Preparation of age-resisting polymers by reactions involving use of aminomercaptans

ABSTRACT

This invention relates to polymers which contain amino-sulfide age-resistant groups, and their preparation by reaction of aminomercaptans.

This is a Continuation of application Ser. No. 471,076 filed on Mar. 1,1983 (now issued as U.S. Pat. No. 4,760,181) which is a continuation ofprior application Ser. No. 286,494 filed on Jul. 24, 1981 now abandoned,which is a continuation of prior application Ser. No. 144,153 filed onApr. 28, 1980 now abandoned, which is a continuation of priorapplication Ser. No. 050,021 filed on Jun. 18, 1979 now abandoned, whichis a continuation of prior application Ser. No. 845,001 filed on Oct.25, 1977 now abandoned which is a continuation-in-part of priorapplication Ser. No. 712,551 filed on Aug. 9, 1976 now abandoned.

PRIOR ART

Kline U.S. Pat. No. 3,658,769 discloses polymers containing relativelylow levels of certain N,N'-disubstituted p-phenylenediamine unitschemically bound to polymers as substituents of acrylic monomer unitspresent in them, which units have resistance to aging at elevatedtemperatures. This resistance is not possessed by similar polymers notcontaining such substituents. The age-resisting functions are introducedinto the polymers by copolymerization of acrylic monomers containingsuch functions with vinyl or dienic monomers to prepare the polymersystem.

A review article by Meyer, Tewksbury and Pierson in HIGH POLYMERS, Vol.XIX, E. M. Fetles, Ed., Interscience, New York, 1964, Chapter 2,discloses the incorporation of aliphatic mercaptans into polydienes tovarying degrees by many workers and that the reaction involved wasaddition of the mercaptan to a polymeric double bond. The degrees towhich the resultant adducted polymers differed in properties from thepolymeric reactants depended on the degree of interaction.

THE INVENTION

This invention relates to polymers self-resistant to aging which containN,N'-disubstituted-p-phenylene-diamine groups bound to the respectivepolymers by monosulfide linkages. It also relates to methods ofpreparing such compositions by interactions of certain aminomercaptanswhich are N,N'-disubstituted p-phenylene diamines, each containing amercapto alkyl function, either with a polymer radical during the courseof a free-radical polymerization, or with a polymer containing at leastone olefin unit per molecule in a post-polymerization addition reaction.Aminomercaptans which are useful in the process are discussed under theheading The Aminomercaptans.

It is well known that certain N,N'-disubstituted p-phenylene diaminederivatives, when used at relatively low weight levels, as additives tocertain oxidizable oils, fats or polymers, greatly enhance theresistance to aging or to oxidation of these materials. Hence, byincorporating a compound containing such a diamine substituent into apolymer by means of a chemical bond, one makes such a polymerintrinsically resistant to aging. Such age resistance cannot be removedfrom the polymer by extraction, sublimation, decantation, filtration orby other physical process by which conventional antioxidant additivescan be removed from polymers.

According to the present invention, an aminoantioxidant function isincorporated into a polymer at relatively low levels by interaction ofrelatively low levels of a non-monomeric amino-substituted mercaptaneither (a) as a chain transfer reagent reacting both with monomer andwith growing polymer radicals during the course of a free radicalpolymerization or (b) in an addition process in which it reacts with apreformed polymer containing at least one double bond or (c) in areaction with a polydiene homopolymer or copolymer during the course ofmilling and curing. All such interactions may be carried out either inemulsion, solution, dispersion, or bulk media.

The polymer compositions prepared by the processes of this invention arepreferable to known similar polymer compositions not containingchemically bound age-resisters but protected by conventionalage-resisters.

Hence polymers containing such chemically bound age-resister groups havea distinct advantage over polymers of similar structure but protectedonly by admixture with conventional age-resister compounds.

The polymers with built-in age-resistance are usually composed ofsegmers of conjugated diene monomers of 4 to 10 carbon atoms ornon-conjugated cyclic or acyclic olefin monomers of 2 to 20 carbon atomsor vinyl monomers of 2 to 10 carbon atoms.

Examples of the products made from the new polymers with built-inage-resisters include rubber goods such as liners, gaskets, hoses andbelts subjected to elevated temperatures and/or in contact with oils orsolvents, and foam-rubber backings for carpets subjected todry-cleaning, etc.

The products with built-in age resistance may be liquid or elastomericsolid. They may be elastomers or more resinous, depending upon thenature of the monomer used and the molecular weight, etc., and nolimitation is placed on the molecular weight. Those which are elastomersmay, when compounded with vulcanizing ingredients, be vulcanized andused wherever rubbers are employed. Some of these may be used as gums,when not vulcanized. Depending upon the nature of the polymer, it may beused for coatings for wood, fabrics, metals, etc., for caulkings,moldings, etc.

The amount of the age-resisting group united with the polymer isgenerally comparable to the amount of conventional antioxidant orantiozonant employed, being generally between 0.10 and 10 parts, andpreferably 0.5 to 5 parts per 100 parts of the polymer. The amount mayvary depending upon the particular aminomercaptan, the nature of thepolymer, and the use to be made of the product. For instance, aninstallation in the tropics will require more than the same installationwhich is to be installed in a cold climate.

One process of the present invention involves a chain-transfer reaction,in which certain mercapto-alkyl derivatives ofN,N'-disubstituted-p-phenylene diamines which have antioxidantproperties interact with a polymerizing monomer system to producepolymers containing these diamino substituents interlinked with thepolymer through a monosulfide bond. This is discussed below under theheading The Chain Transfer Reaction. The resultant polymer has anintrinsic age resistance. Such polymers may be produced by polymerizingany monomers or mixtures of monomers capable of homopolymerization,copolymerization or interpolymerization by free-radical mechanism inpresence of such diamine derivatives. Such monomers include conjugateddienes containing 4 to 6 or more up to, for example, 10 carbon atoms,and halogen derivatives thereof, including butadiene-1,3-;2-ethylbutadiene-1,2,3-dimethyl-butadiene-1,3; isoprene; piperylene;1,3-hexadienes; 1,3-decadienes; and 2-chlorobutadiene; etc., and vinylicmonomers containing 2 to 10 carbon atoms including styrene, alpha-methylstyrene, divinyl benzene, vinyl chloride, vinyl acetate, vinyl pyridine,vinylidene chloride, acrylonitrile, methacrylonitrile, ethyl acrylate,methyl methacrylate, acrylic acid, methacrylic acid, maleic acid,itaconic acid, and maleic anhydride, etc.

Another process of the present invention involves another free-radicalreaction of a member of the same family of aminomercaptans with polymersubstrates which contain at least one reactable double bond per polymermolecule. This is an addition reaction in which the aminomercaptanreacts with this double bond. This is discussed below under the headingThe Free-Radical Addition Reaction.

Thus, any isotactic, syndiotactic or atactic homopolymer or copolymerwhich contains a double bond reactable with the operable aminomercaptanscan be used as a substrate in carrying out this addition process.

A third process relates to interaction of any of the foregoing polydienehomo- and co-polymers with said aminomercaptans during the course ofmilling and curing in the presence of rubber chemicals includingreinforcing agents and pigments, etc. Because the reaction takes placeduring milling and curing, the exact nature of the reaction is notclearly evident but a vulcanized product is obtained which isintrinsically age-resistant. This is further discussed under the headingMilling and Curing Process.

In this process, a small amount of the aminomercaptan is used, such as0.10 to 5 parts, more or less. The temperature may vary widely. If themilling is conducted at a sufficiently high temperature, some or all ofthe reaction may be completed before curing. The curing operation willbe employed at any usual temperature, and the time required will dependupon the polymer system, the temperature and the curing system.

THE AMINOMERCAPTANS

The aminomercaptans useful in producing the age-resisting polymers ofthis invention are defined by the following formula; ##STR1## which issometimes referred to as ZSH. In this function R=a radical of the classconsisting of (a) phenyl or phenyl which is substituted in any one ormore positions with an alkyl or alkoxy group of 1 to 4 carbon atoms orwith a radical of the formula ##STR2## in which both R₇ and R₈ may beeither an alkyl group of 1 to 4 carbon atoms or hydrogen; or (b) acycloalkyl radical having from 5 to 12 carbon atoms; or (c) a branchedacyclic group comprising a chain of 1 to 12 carbon atoms, and eachcarbon may be substituted with 1 or 2 alkyl groups of 1 to 3 carbonatoms; or (d) an alicyclic aralkyl or aryl radical having from 7 to 14carbon atoms.

m=zero or 1

n=0 to 12

R₁, R₂, R₃, R₄, R₅ and R₆ are each selected from the group consisting ofhydrogen and alkyl groups of 1 to 5 carbon atoms; and may be the same ordifferent.

The aminomercaptan may be prepared by various methods. A p-phenylenediamine substituted at one nitrogen atom with the desired aryl or alkylsubstituents, RNH.C₆ H₄.NH₂, may be converted to an N-mercapto alkylacyl derivative, RNH.C₆ H₄.NHC=O(CH₂)_(n) SH by direct amidation with amercapto acid such as thioglycolic or beta-mercaptopropionic acid.Illustrations of such preparations are included as Example 1.N-Mercaptoalkyl derivatives of similarly substituted p-phenylenediamines (as illustrated in Formula 1 where m=zero) may be prepared fromthe latter by treatment with ethylene sulfide or propylene sulfide, or,in a two-step procedure involving treatment of an N-substitutedphenylene diamine with a half mole equivalent of a dithio dialdehydesuch as α, α'-dithioisobutyraldehyde to form a dithio diimine [aprocedure described by J. J. D'Amico and W. E. Dahl, J. Org. Chem. 40,1224 (1975)]; and subsequent reduction of the diamine to anaminomercaptan with lithium aluminum hydride in refluxingtetrahydrofuran [a procedure described by J. L. Corbin and D. E. Work,J. Org. Chem. 41, 489 (1976)] or some other reducing system. Such aprocedure is illustrated by Example 3.

The method of preparing the aminomercaptans useful in this invention isnot critical to the practice of this invention.

Representative amino-mercaptans which can be used in the presentinvention are listed below and the numbers refer to the numbers in TableI.

    ______________________________________                                        NO.    NAME                                                                   ______________________________________                                        I      N-(4-anilino-phenyl)-α-mercapto-acetamide                        II     N-(4-anilino-phenyl)-βmercapto-propionamide                              N-(4-anisidino-phenyl)- or N-(4-phenetidino-                                  phenyl)-α-mercapto-acetamide                                     V      N-(4-anisidino-phenyl)-β-mercapto-propionamide                           N-(2-toluidino-phenyl)-α-mercapto-acetamide                      IV     N-(2-toluidino-phenyl)-β-mercapto-propionamide                    III    N-(4-toluidino-phenyl)-α-mercapto-acetamide                      VI     N-[4-(α',Υ'-dimethyl-butylamino)-phenyl]-α-mer-           1                                                                             capto-acetamide                                                        VII    N-[4-(α',Υ'-dimethyl-butylamino)-phenyl]-β-mer-            8                                                                             capto-propionamide                                                            N-(4-anisidino-phenyl)-mercapto-propionamide                                  N-(4-phenetidino-phenyl)-β-mercapto-propionamide                         N-(4-cyclopentylamino-phenyl)-α-mercapto-                               acetamide                                                                     N-(4-cyclohexylamino-phenyl)-α-mercapto-                                acetamide                                                                     N-(4-cyclohexylamino-phenyl)-ω-mercapto-                                lauramide                                                                     N-(4-cyclooctylamino-phenyl)-ω-mercapto-                                caproamide                                                                    N-(4-cyclodecylamino-phenyl)-β-mercapto-                                 isobutyramide                                                                 N-(4-cyclododecylamino-phenyl)-β-mercapto                                capramide                                                                     N[4-(α'-methyl-undecylamino)-3-isopropyl-6-                             methyl-phenyl]-α-mercapto-butyramide                                    N-(4-anilino-phenyl)-β-mercapto-β-β-dimethyl-                  butyramide                                                                    N-[α',Υ'-benzylamino-phenyl]-β-mercapto-propion-           .                                                                             amide                                                                         N-[4-(α'-methyl-benzylamino-phenyl]-α-mercapto-                   acetamide                                                                     N-[4-(α'-methyl-benzylamino)-phenyl]-β-propon-                     amide                                                                         N-[4-(α'-ethyl-Υ'-methyl-pentylamino)-phenyl]-                  α-mercapto-acetmide                                                     N-[4-α'-(ethyl-Υ'-methyl-pentylamino)-phenyl]-                  β-propionamide                                                           N[4-dimethylamino-phenyl]-ω-mercapto-myristamide                        N-[4-diethylamino-phenyl]-α-mercapto-acetamide                          N-[4-di-n-butylamino-phenyl]-α-mercapto-                                propionamide                                                           ______________________________________                                    

Another amino mercaptan which is described in Example 3 as compound XIVis:

XIV N-(β-mercapto-β,β-dimethyl-ethyl), N'-phenyl-p-phenylenediamine

Other amino mercaptans include:

N-(β-mercapto-β,β-dimethyl-ethyl)N'-(4-di-n-butyl-phenyl)p-phenylenediamine

N-(δ-mercapto-butyl)-N'-phenyl-p-phenylene-diamine

N-(ω-mercapto-lauryl)-N'-phenyl-p-phenylene-diamine

Other compounds include those in which m=o, corresponding to the manycompounds listed above in which m=1.

Examples of diamine substrates suitable for preparation ofamino-mercaptans useful in this invention, described and referred to bynumber in Table II, are:

VIII N-phenyl-p-phenylenediamine

X N-2'-tolyl-p-phenylenediamine

XIII bis-[β-(4-anilinophenyl-imino)-α,α-dimethylethyl] disulfide

N-4'-phenethyl-p-phenylenediamine

IX N-4'-tolyl-p-phenylenediamine

XI N-4'-anisyl-p-phenylenediamine

XII N-(α',α'-dimethyl-butyl)-p-phenylenediamine

N-(4'-dimethylamino-phenyl)-p-phenylenediamine

The aminomercaptans may be used as antioxidants following conventionalprocedures.

Within the family of aminosulfide groups illustrated by ZS- group ofFormula 1, there is a sub-family of amino groups having the essentialstructural features of certain diamines which are used commercially asantiozonants. These are those amino groups in which at least one of thenitrogen atoms of the para-phenylenediamine group is substituted by analkyl group through a secondary or tertiary carbon atom (a condition ofFormula 1 in which m=0, and at least either R₃ or R₄ is an alkyl grouprather than hydrogen) and the other nitrogen atom of this diamine groupis attached either to an alkyl, a phenyl, or substituted phenyl group,through a secondary or tertiary carbon atom (a carbon atom having nomore than one hydrogen atom substituent). This sub-family ofaminosulfide groups provides polymers to which these groups are attachedwith an appreciable degree of resistance to ozone cracking in additionto an enhanced resistance to attack by other forms of oxygen.

1. THE CHAIN TRANSFER REACTION

According to one reaction, a mercaptoalkyl derivative of anN,N'-disubstituted diamine is chemically incorporated into the polymerby a monosulfide bond by means of a chain transfer reaction. The stepsof the reaction are represented by the following equations:

    I.sup.. +M←→IM.sup..                           EQUATION 1

    IM.sup.. +nM←→IM.sub.n+1.sup.. =P.sub.x.sup..  EQUATION 2

    P.sub.x.sup.. +ZSH←→P.sub.x H+ZS.sup..         EQUATION 3

    ZS.sup.. +M←→ZSM.sup..                         EQUATION 4

    ZSM.sup.. +qM←→ZSM.sub.q+1.sup.. =Py.sup..     EQUATION 5

    Py.sup.. +ZSH←→PyH+ZS.sup..                    EQUATION 6

In these equations:

I.sup.. =the activating initiator radical

M=the reacting monomer (as defined earlier for the chain transferprocess)

n and q=numbers of molecules of monomer reacting with initial monomerradical

P_(x).sup.. represents the relatively small number of polymer radicalsgenerated initially

Py.sup.. represents the majority of polymer radicals formed, which arechemically bonded to an amino group through a sulfide linkage

ZSH=a member of the family of aminomercaptans used, in which thestructure ZS is defined in further detail by the aminosulfide groupillustrated in Formula 1.

An illustration of such a chain transfer reaction as a mode ofincorporation of an aralkyl sulfide group into polymers is given in thestudy of the interaction of 2-mercaptomethyl naphthalene with apolystyrene radical, which is to be found in an article of Pierson,Costanza and Weinstein in J. POLYMER SCIENCE, 17, 221, (1955).

In the use of the chain transfer method of chemical incorporation ofamino antioxidant functions into polymers, one or more monomers known topolymerize under free radical conditions may be polymerized in thepresence of a low level of one of the amino mercaptans useful in thisinvention. The polymerizations may be carried out in emulsion,suspension, bulk or solution type systems. Some adjustments in thepolymerization recipe and/or conditions are necessary to assure that asatisfactory rate of polymer formation and a desirable polymer molecularweight level are achieved. Among the parameters critical to achievementof the process are the level of aminomercaptan charge, which may have aneffect on the degree of inhibition of polymerization as well as a verydefinite effect both on the level of age-resistor function incorporatedinto the polymer and on the average molecular weight of the resultantpolymer. Other adjustments which may be required in order to achievesuch goals are the choice of a free radical initiator system which doesnot pre-oxidize the aminomercaptan into a substance which greatlyretards or prevents polymerization, and the possible use of a solvent ordiluent additive including use of a comonomer chosen to assure thesolubility of the amino-mercaptan in the polymerization system. Inemulsion systems, some solvents such as pyridine or toluene, or smallamounts of such comonomers as styrene, acrylonitrile or acrylic esterscan be used to advantage for the latter purpose.

Examples of free-radical initiator systems useful in the practice of thechain transfer process include those known as "redox" systems. Anexample is those initiators which employ a combination such as achelated ferrous salt, sodium formaldehyde sulfoxylate and an organichydroperoxide such as cumene or para-menthane hydroperoxide.

Thermally dissociative compounds may also be used as polymerizationinitiators for this process. Those dissociative initiators which are notcapable of oxidizing the aminomercaptans, such as azo compounds, forexample, α,α'-azobis-isobutyronitrile andα,α'-azobis(α,γ-dimethyl-valeronitrile), are preferable overdissociative peroxy initiators, such as ammonium persulfate or tertiarybutyl-peroxy isobutyrate which are less effective.

The reaction may be carried out in solution. If an emulsifier isemployed, a suitable emulsifier is selected. Other components such asbuffers (to control the pH) may be used. Suspending agents are used, ifdesired. These and other components such as coloring agents, etc. may beused in desired amounts.

The temperature will depend upon the initiator used, etc. In the "redox"system, the temperature will generally vary between 0° and 50° C. Usingthermally dissociative initiators, the temperature will vary from about30° to 100° or 120° C., more or less, depending upon the half life ofthe initiator and the particular monomer system.

2. THE FREE-RADICAL ADDITION REACTION

This procedure is an addition reaction for introducing the age-resistinggroup into a polymer. It involves the interaction of an arylamino alkylmercaptan with a polymer containing at least one vinylic double bond orinternal double bond per polymer molecule. This interaction is similarto the well-known addition of methyl mercaptan molecules to the olefinunits of polydienes to form wholly or partially saturated additionproducts which contain methyl sulfide substituents. (See the article byMeyer, Tewksbury and Pierson in HIGH POLYMERS, Vol. XIX E. M. Fettes,Ed., Interscience, New York, 1964, Chapter 2, starting on page 133.There are foreign patents relative to the reaction.)

The stereochemical nature of polymers useful in this addition reactionmay vary widely and they include polymers made from monomers containing2 to 20 carbon atoms. They include isotactic, syndiotactic and atacticpolydiene homopolymers and copolymers with other conjugated ornon-conjugated dienes or vinyl monomers. The method of preparation ofsuch polymers is not important as long as the reactability of at leastone olefin unit per polymer molecule is maintained. Polymers applicableinclude naturally occurring polydienes such as natural rubber, guttapercha, balata as well as those prepared synthetically from monomers.Preparation of such polymer may be initiated thermally, by radiation orby a variety of catalysts including free-radical initiation systems orcationic, anionic or coordination complex catalysts including theZiegler-Natta type.

Included among the polymeric substrates operative in this process arefree-radical polymers prepared from the same monomers or mixtures ofmonomers which can be used in the previously described chain-transferprocess as long as the resultant polymers contain at least one reactableolefin unit per polymer molecule. Also included are polymers ofethylene, propylene or isobutylene containing small amounts of segmersof conjugated or non-conjugated acyclic or cyclic dienes or polyolefinsincluding isoprene, butadiene-1,3; 1-norbornene, and 1,5-cyclooctadiene.

Included among operative polymeric substrates prepared by non-freeradical techniques are cis and trans forms of 1,2-polybutadiene or1,4-polybutadiene as well as syndiotactic or atactic homopolymers orcopolymers prepared from butadiene-1,3; cis and trans forms of3,4-polyisoprene or 1,4-polyisoprene as well as syndiotactic or atactichomopolymers or copolymers prepared from isoprene; analogous preparablehomopolymers or copolymers of 2-ethyl-butadiene-1,3; piperylene;2,3-dimethyl-butadiene; 2-chloro-butadiene-1,3; or 1,3-hexadienes.

Other polymers which may be used as substrates include those prepared bymetathesis reactions of cyclo-olefins, cyclo-diolefins,bicyclo-monoolefins and bicyclo-diolefins, mixtures of these withα-olefins or copolymers of these with α-olefins, or norbornene. By themetathesis reaction is meant a polymerization in which the substituentson the olefin carbon atoms of one monomer molecule are interchanged withthose of another monomer molecule. Polymers so prepared includepolypentenylene, polyoctenylene, or polyoctadienylene.

Polymers prepared by ring opening reactions of certain cyclic olefinssuch as norbornene by a non-metathesis catalyst such as a cationic orZiegler-Natta type catalyst may also be used as substrates for thisprocess.

In the interaction of an aminomercaptan with a double bond alreadypresent in a polymer, this interaction may be carried out in variousways. The polymeric substrate may be dispersed in an emulsion,suspension or solution. The addition reaction is catalyzed byfree-radical initiators, either of the thermally dissociated type or the"redox" type, preferably the former, and including azo compounds such asbis-azoisobutyronitrile and hydroperoxides such as cumene hydroperoxideand p-menthane hydroperoxide. Temperatures necessary for effectiveadditions of the aminomercaptans of this invention to polymericsubstrates are those necessary for continuous dissociation of theparticular catalyst used, and vary from about 0° C. to about 100° C. Thetime of reaction required depends upon many factors including thecatalyst used, its concentration, the level of mercaptan additionrequired and for the case of addition to stereospecific polydienes, theacceptable degree of isomerization of polymer configuration.

In the addition reaction the level of aminomercaptan charged may be from0.1 to 10.0 parts or preferably 0.5 to 5 parts per hundred parts ofpolymer (p.h.p.), and the level of catalyst, if thermally dissociative,may be from 0.05 to 5, and preferably 0.05 to 1.0 p.h.p. The reactiontemperature, using a thermally dissociative catalyst, may be 20° to 120°C., and is preferably 30° to 80° C. The polymer system should be free ofappreciable levels of reactable olefinic monomers and of free-radicalinhibitors in order to obtain a desired level of mercaptan addition inreasonable time. Such reactions can be carried out in emulsion,suspension or solution media.

3. THE MILLING AND CURING PROCESS

In this process, the aminomercaptan is added to a millable elastomericdiene homopolymer or copolymer on a rubber mill, for example a Banbury,in presence of chemical additives used conventionally for curing orvulcanizing rubber, in the presence of air and at conventional rubbermilling temperatures, in the presence or absence of reinforcingpigments. Such rubber stock is then cured in an oven or press at atemperature normally used in the art for production of a vulcanizate, asfor example, between 250° F. and 350° F.

Representative polymers and copolymers useful in the process includepolybutadiene, polyisoprene, isoprene-styrene, butadiene-styrene,isoprene-acrylonitrile, butadiene-acrylonitrile (referred to herein aselastomers) in which a major portion is butadiene or isoprene. Thevulcanizate when extracted with a solvent such as acetone or methylethyl ketone in order to free it of non-rubber additives, has aresistance to oxidation or aging very much greater than that of avulcanizate which has been prepared in the presence of a conventionalantioxidant, such as 2,6-di-t-butyl-p-cresol which has been removed fromthe vulcanizate by extraction. Incorporation of age-resistor functionsby this process is illustrated by Example 11. It is therefore evidentthat the aminomercaptan used is incorporated into such a polymervulcanizate during the combined milling/curing process.

AGE-RESISTANT POLYMERS

The age-resistant polymers of this invention obtained by the severalprocesses described may be defined by the formula ZSP in which ZS is theaminosulfide group of Formula 1, namely, ##STR3## defined above, and P,which has been removed, represents the polymeric portion of theage-resistant polymers referred to herein. Thus, the age-resistantpolymers may be represented by the formula ##STR4## Examples of thepreparation of age-resistant polymers by the chain-transfer reaction areExamples 4,5,6 and 7.

Examples of the preparation of age-resistant polymers by the additionreaction are Examples 8 and 9.

Example 10 illustrates the incorporation of age-resistant aminosulfidegroups into the polymers by milling and curing.

Example 11 illustrates the use of aminomercaptans of this invention asconventional age resisters.

Examples of the preparation of some of the aminomercaptans useful inthis invention, and intermediates used in their preparation, areillustrated by Example 1, 2 and 3.

EXAMPLE 1 N-(4-Anilino-Phenyl)-β-Mercaptopropionamide

A mixture of 18.4 grams of N-phenyl-p-phenylene diamine, 10.6 grams ofβ-mercaptopropionic acid and 120 milliliters of xylene (technical grade)was heated to reflux (about 140° C.) under nitrogen atmosphere, withstirring. A 1.6 milliliter quantity of water (90% of theory) was removedfrom this mixture by azeotropic distillation through a Vigreux columnwith the aid of a Dean-Stark trap, during a 13-hour period. A solidproduct was isolated in 18.7 grams quantity from the reaction mixture bycooling the latter, pouring into hexane, collecting the resultantcrystalline product by filtration, washing the crushed crystallineproduct with more hexane and evaporating to dryness. The product wasrecrystallized from hot toluene to 17.6 grams (64.5%) of white plateletsmelting at 98.3°-99.5° C. The resultant new compound,N-(4-anilino-phenyl)beta-mercaptopropionamide, sometimes referred tohereafter as MPDA, had mercaptan assay of 93.8% of theoretical, on thebasis of a potentiometric titration with an isopropyl alcohol solutionof silver nitrate, following a method described by R. M. Pierson, A. J.Costanza and A. H. Weinstein, J. Polymer Sci., 17, 234 (1955).

In a manner similar to that described above, a series of aminomercaptanswere prepared by use of the appropriate diamine and mercapto-acidsubstrates. They are characterized in Table I. Those products which didnot crystallize readily were freed of mercapto-acid substrate byextracting their benzene solutions with aqueous sodium carbonate, andthen with water before isolating.

                                      TABLE I                                     __________________________________________________________________________    AMINOMERCAPTAN                                                                STRUCTURE                    CHARACTERISTIC                                    ##STR5##                     MELTINGSTATE OR                                                                      Sulfur, %                                                                             Nitrogen, %                      NO.                                                                              R           n       COLOR POINT, °C.                                                                    Calcd                                                                             Found                                                                             Calcd                                                                             Found                                                                             RSH,                      __________________________________________________________________________                                                        %                         I  Phenyl      1       White 135.5-136.5                                                                          12.4                                                                              12.3                                                                              10.8                                                                              10.8                                                                              90.1                      II Phenyl      2       Silver                                                                              98.3-99.5                                                                            11.8                                                                              11.8                                                                              10.3                                                                              10.3                                                                              93.8                      III                                                                              p-Tolyl     1       Brown 229.0-230.0                                                                          11.2                                                                              20.5                                                                              9.72                                                                              9.62                          IV c-Tolyl     2       Brown Syrup                  71.6                      V  p-Anisyl    2       Blue-grey                                                                           124-126                73.9                      VI 1,3-Dimethyl-                                                                             1       Amber Glass                  69.6                         butyl                                                                      VII                                                                              1,3-Dimethyl-                                                                             2       Black Glass                  61.7                         butyl                                                                      __________________________________________________________________________

EXAMPLE 2 Alkyl- or Aryl-Substituted-p-Phenylenediamine Substrates

The diamine substrates used for preparation of the aminomercaptans ofTable I and the aminomercaptan XIV, whose preparation is described inExample 3, are characterized in Table II. Referring to the examples ofTable II, they were either available as the free amine (VIII) or itshydrochloride (XI). Compounds IX and X were prepared fromp-nitrochlorobenzene and the appropriate toluidine according to a methoddescribed by R. H. Kline, RUBBER CHEM. TECHNOL. 46, 96 (1973). CompoundXII was prepared by reductive alkylation of p-amino-acetanilide withmethyl isobutyl ketone according to a general procedure discussed byMorris Freifelder in PRACTICAL CATALYTIC HYDROGENATION,Wiley-Interscience, New York, 1971, Ch. 17, page 346.

                  TABLE II                                                        ______________________________________                                        DIAMINE SUBSTRATES                                                                                        USED FOR                                               STRUCTURE              PREPARATION OF                                         RNH   NH.sub.2                                                                            MELTING    AMINO-MERCAPTAN                                   NO.  in which R =                                                                              POINT, °C.                                                                        NUMBER:                                           ______________________________________                                        VIII Phenyl      76-77      I, II, XIV                                        IX   p-Tolyl     115-116    III                                               X    o-Tolyl     58.5       IV                                                XI   p-Anisyl    102-103    V                                                 XII  1,3-Dimethyl-                                                                             43-44      VI, VII                                                butyl                                                                    ______________________________________                                    

EXAMPLE 3 (-(Beta-Mercapto-Beta, Beta-Dimethyl-Ethyl),N'-Phenyl-Para-Phenylenediamine

An intermediate compound,bis-[beta-(4-anilinophenyl-imino)-alpha,alpha-dimethylethyl] disulfidewas first prepared as follows:

Following a procedure described for preparation by J. J. D'Amico and W.E. Dahl, J. Org. Chem., 40 1224 (1975), α,α'-dithiobis-isobutyraldehyde,which was freshly prepared as described from isobutyraldehyde and sulfurmonochloride, were interacted with two mole equivalents ofN-phenyl-p-phenylenediamine (VIII), at ambient temperature, in methanolsolvent. The product, obtained in 89 per cent yield, from a water-washedbenzene extract of the reaction mixture was a dark-brownuncrystallizable semi-solid form ofbis-[beta-(4-anilophenyl-amino)-alpha, alpha-dimethylethyl] disulfide.

This diamino disulfide was reduced to a mercaptan as follows: A solutionof 39.2 grams of compound (prepared as above) in 150 milliliters ofanhydrous tetrahydrofuran was added dropwise, with stirring, under inertatmosphere, to a refluxing solution of 5.0 grams of lithium aluminumhydride in 200 more milliliters of the same solvent; over a 40-minuteperiod. The reaction mixture was permitted to reflux for several morehours. The conditions used for this reaction and the subsequent productwork-up are in accordance with conditions described for preparation ofanalogous compounds by Corbin and Work, J. Org. Chem. 41, 489 (1976).The excess LiAlH₄ was decomposed with aqueous sodium potassium tartrate,and the product isolated from a water-washed diethyl ether extract byvacuum evaporation. In this manner, 37.2 grams of a thick dark-brownsyrup, containing 47 percent of mercaptan, namely,N-(beta-mercapto-beta,beta-dimethyl-ethyl),N'-phenyl-para-phenylenediamine, Compound XIV ofTable II, having the theoretical molecular weight of 272, was isolated.

EXAMPLE 4 Incorporation of Aminomercaptans into Polystyrene VIA ChainTransfer Reaction

In two separate experiments, 1.00 part by weight of Compounds I or II ofTable I, corrected for active mercaptan content, was charged into vialseach containing 100 parts of styrene, 0.10 part ofbis-azoisobutyronitrile and 5.0 parts of pyridine. In a third vial, thesame proportions of all ingredients except aminomercaptan were charged.The vials were sealed under nitrogen atmosphere and tumbled for 16 hoursin a water bath at 50° C. Low conversions of polystyrene samples wereisolated from each of the three solutions by coagulating into isopropylalcohol.

On the basis of inherent viscosity determinations made on benzenesolutions of dried polystyrene samples, the number average molecularweights were determined for each sample, using an equation developed byF. R. Mayo, J. Am. Chem. Soc. 65, 2324 (1943).

In this way, it was determined that polymer made in the presence ofCompound II (MPDA) had a molecular weight of 17,100 as compared with avalue of 266,000 for the control polymer. By substituting thesemolecular weight values into an equation developed by the cited author,a chain transfer constant (T.C.), representing a ratio of reactivity ofCompound II over that of a styrene monomer molecule with a polystyreneradical, was calculated. The fact that the T.C. value for Compopund IIat 50° C. obtained in this manner was an appreciable value, namely 1.40,indicated that Compound II had reacted appreciably with the polymer bymeans of an incorporating mechanism. By similar means, it was shown thatCompound I (MADA), with a T.C. value of 0.27, had an appreciable, ifsomewhat lesser, tendency to incorporate into polystyrene.

EXAMPLE 5 Incorporation of MPDA into Isoprene/Styrene Copolymers byChain Transfer Reaction

A series of emulsion copolymerizations A to E were carried out infour-ounce screw-cap bottles using 20.0 grams monomer charges andcontaining the following ingredients in common, all listed in parts perhundred of monomer:

    ______________________________________                                               Isoprene                                                                              75.0                                                                  Styrene 25.0                                                                  Pyridine                                                                              5.00                                                                  Potassium                                                                             5.00                                                                  stearate                                                                      Distilled                                                                             200                                                                   water                                                                  ______________________________________                                    

Variable ingredients were also charged into these bottles, as indicatedin Table III on a parts per hundred of monomer basis. Conversion levelsobtained, after the bottles were swept with nitrogen, sealed and tumbledfor 17 hours in a water bath at the prescribed temperatures, are alsorecorded in this table.

                  TABLE III                                                       ______________________________________                                        VARIABLES         A      B      C    D    E                                   ______________________________________                                        Ammonium persulfate                                                                             --     0.40   0.40 --   --                                  Azobis-isobutyronitrile                                                                         0.40   --     --   0.40 0.40                                MPDA.sup.a        --     2.00   2.00 --   2.00                                Reaction temperature, °C.                                                                50     50     70   70   70                                  Conversion to polymer, %                                                                        76     0      26   97   80                                  ______________________________________                                         .sup.a On basis of 100% mercaptan activity.                                   Efficiency of incorporation of MPDA into isoprene/styrene copolymers     

A series of copolymers of substantially 75% of isoprene: 25% styrenewere prepared as in Example 5, recipe D, with variables indicated inTable IV including MPDA charge levels. Polymers were coagulated intoisopropyl alcohol, freed of non-polymeric substances by repeatedextractions with hot isopropyl alcohol, and vacuum evaporated.

Levels of 4-anilinophenyl-carbamyl units incorporated into polymers, ona parts per hundred (p.h.r.) basis, were determined on basis of acolorometric assay of the intensity of blue-colored quinone-iminechromophore developed by oxidation of chlorofrom solutions of polymerswith benzoyl peroxide.

Thin films of polymers of known weight of from 1 to 1.5 grams were madeby evaporating benzene cements of polymers onto tared aluminum sheetshaving a surface area of 1500 cm². These sheets were inserted into thechambers of a typical oxygen absorption apparatus. Oxidation resistance(O.R.) values for these polymers were determined as the number of hoursrequired for absorption of 1 per cent by weight of oxygen by a polymersample from oxygen atmosphere at a given temperature, in this case 90°C.

Data relating to efficiency of incorporation of amino groups and tooxidation resistance of these polymers are also included in Table IV.Data shows the marked enhancing effect of incorporated MPDA on polymeroxidation resistance.

                  TABLE IV                                                        ______________________________________                                                     PARTS BY WEIGHT IN                                               RECIPE VARIABLES                                                                             F      G       H     J     K                                   ______________________________________                                        MPDA           1.00   2.00    3.00  2.00  --                                  n-Dodecyl mercaptan                                                                          --     --      --    --    1.5.sup.a                           Pyridine       5.-    5.0     5.0   --    5.0                                 POLYMERIZATION RESULTS:                                                       Conversion, %  87     80      18    94    92                                  P'z'n time, hrs. at 70° C.                                                            17     17      17    17    7                                   4-Anilinophenyl-carbamyl                                                                     0.52   0.76    1.06  --    --                                  units incorporated, p.h.r.                                                    Efficiency of MPDA                                                                           52     38      35                                              incorporation.sup.b, %                                                        O.R. Values at 90° C.                                                                 92     520     405   500   8.6                                 ______________________________________                                         .sup.a Added to insure polymer solubility in benzene.                         .sup.b On basis of parts MPDA charged.                                   

EXAMPLE 6 Incorporation of Other Aminomercaptans into Isoprene/StyreneCopolymers by Chain Transfer Reaction

Using the general procedure of Example 5, but substituting for MPDA,2.00 part quantities of other aminomercaptans characterized in Table I,and adjusting for mercaptan activity, a series of 75.0 isoprene/25.0styrene mixtures were polymerized for 17 hours at 70° C. Polymers wereisolated, worked up and tested in the manner indicated in Example 5.Parameters relating to polymerization and to polymer characteristics areindicated in Table V.

                  TABLE V                                                         ______________________________________                                                    L    M      N      P    Q    R                                    ______________________________________                                        Aminomercaptan                                                                              I      IV     V    VI   VII  XIV.sup.a                          number (see Table                                                             I or II)                                                                      Conversion, % 56     53     75   29   99   27                                 P'z'n time, hrs.                                                                            22     16     21   17   17   16                                 at 70° C.                                                              O.R..sup.a values at 90° C.                                                          95     420    515  380  245  220                                ______________________________________                                         .sup.a Charging only 1.00 pt. of aminomercaptan.                              O.R. = OxidationResistance: Determined as in Example 6.                  

EXAMPLE 7 Incorporation of Aminomercaptans I and II into ButadieneCopolymers Via Chain Transfer Reaction

Butadiene mixtures with either acrylonitrile or methyl methacrylateweighing 20.0 grams each were polymerized in four-ounce screw-capbottles in presence of 1.60 part amounts of aminomercaptans as indicatedin Table VI, along with control polymers. Recipes used contained thereduction-oxidation ("redox") type initiator systems indicated in TableVI. Also included in this table are conversion levels of the resultantpolymers and their oxidation resistant values after removal ofnon-polymeric substances by extraction.

                  TABLE VI                                                        ______________________________________                                                   PARTS BY WEIGHT IN:                                                INGREDIENTS: T       U       V     W     X                                    ______________________________________                                        Butadiene    67.0    67.0    67.0  80.0  80.0                                 Acrylonitrile                                                                              33.0    33.0    33.0  --    --                                   Methyl methacrylate                                                                        --      --      --    20.0  20.0                                 Tetiary dodecyl                                                                            --      --      0.8   --    0.5                                  mercaptan                                                                     MADA (I).sup.a                                                                             1.60    --      --    --    --                                   MPDA (II).sup.a                                                                            --      1.60    --    1.60  --                                   Potassium stearate                                                                         5.00    5.00    5.00  --    --                                   Trisodium phosphate                                                                        0.20    0.20    0.20  --    --                                   Sodium linear alkyl                                                                        --      --      --    5.00  5.00                                 sulfonate                                                                     Water        200     200     200   200   200                                  FeSO.sub.4.7H.sub.2 O                                                                      0.042   0.042   0.042 0.042 0.042                                Iron chelating agent.sup.b                                                                 0.17    0.17    0.17  0.17  0.17                                 Sodium formaldehyde                                                                        0.04    0.04    0.04  0.04  0.04                                 sulfoxylate                                                                   Cumene       0.24    0.24    0.24  0.24  0.24                                 hydroperoxide                                                                 Conversion, %                                                                              99      95      99    61    99                                   O.R. values at                                                                             390     385     1     695   5.9                                  100° C., hours                                                         ______________________________________                                         .sup.a Adjusted upward for 100% mercaptan activity.                           .sup.b Active parts of a 34% aqueous solution of a 90/10 mixture of a         tetrasodium salt of ethylenediamine tetracetic acid and the monosodium        salt of N,Ndi-(alpha-hydroxyethyl) glycine, sold as "Versene Fe III".    

The last two ingedients charged into each bottle were the butadiene andthe cumene hydroperoxide. The bottles were prechilled to 0° C. beforeadding the butadiene, swept free of air by venting the excess of thismonomer, and each was sealed with a screw-cap lined with self-sealingrubber and Teflon gaskets. The hydroperoxide was then added through thecap by use of a hypodermic syringe. The bottles were then tumbled in awater bath at 10° C. for 16 hours. Polymer latices were coagulated intoisopropyl alcohol, and the resultant coagula freed of non-polymericmaterial by repeated extractions with hot isopropyl alcohol. Thecopolymers were evaporated to dryness in vacuum, and tested forresistance to oxidation as in EXAMPLE 7, casting nitrile copolymer filmsfrom methyl ethyl ketone and the acrylic ester copolymer films frombenzene. In this instance, the oxidation resistance value determinationwas done at 100° C.

Results, as indicated in Table VI, show that the resistance to oxidationof butadiene acrylonitrile copolymers were greatly enhanced relative toa control, by incorporation of antioxidant groups by the use of eitheraminomercaptan I (MADA) or II (MPDA) and that oxidation resistance of abutadiene/methyl methacrylate copolymer was greatly enhanced over thatof a control by similar incorporation of MPDA.

EXAMPLE 8 Incorporation of Aminomercaptans into Polybutadiene byAddition in Emulsion

A polybutadiene latex was prepared by polymerizing butadiene in an8-ounce screw-cap bottle for 16 hours at 50° C. using the recipeindicated in TABLE VII.

                  TABLE VII                                                       ______________________________________                                        INGREDIENTS       PARTS BY WEIGHT                                             ______________________________________                                        Butadiene         100                                                         Tertiary dodecyl mercaptan                                                                      0.50                                                        K.sub.2 S.sub.2 O.sub.8                                                                         0.10                                                        Potassium stearate                                                                              5.0                                                         Water             200                                                         ______________________________________                                    

The resultant latex was stripped of residual butadiene monomer by gentlydistilling, under nitrogen atmosphere, until no foaming occurred and afew droplets of water condensed.

Two 8-ounce screw-cap bottles were each charged with 72.7 gramquantities of this latex (23.9% solids) containing 20.0 grams of rubber.To each was added 0.25 parts of azobis-isobutyronitrile per hundred ofrubber (p.h.r.). One was charged with 2.00 parts of MADA, the other with2.00 parts of MPDA, both adjusted to 100% mercaptan activity. Bottleswere purged with nitrogen, sealed and tumbled for 16 hours in a waterbath at 50° C.

These latices as well as a sample of untreated polybutadiene latex werecoagulated into isopropyl alcohol, extracted free of nonpolymericadditives, dried and tested for oxidation resistance at 90° C. in themanner described in EXAMPLE 6. On the basis of results indicated inTABLE VIII, it is seen that a considerable degree of intrinsic oxidationresistance has been incorporated into polybutadiene by the use of eitherMADA or MPDA in this process.

                  TABLE VIII                                                      ______________________________________                                        POLYMERS         O.R. VALUES AT 90° C., HRS                            ______________________________________                                        Polybutadiene control                                                                          7.3                                                          Polybutadiene treated with 2.00                                                                62                                                           parts MADA                                                                    Polybutadiene treated with 2.00                                                                58                                                           parts MPDA                                                                    ______________________________________                                    

EXAMPLE 9 Addition of Aminomercaptans to Unsaturated Hydrocabon Polymersin Solution

Samples of cis-1,4-polybutadiene; cis-1,4-polyisoprene; and1,5-polypentenylene, all of which were free of antioxidants and of freeradical inhibitors were dissolved in benzene and treated with 2.00 partsof an aminomercaptan in presence of azobis-isobutyro-nitile (AIBN)catalyst under nitrogen atomosphere at 70° C. under conditions indicatedin Table IX. Polymers were coagulated into isopropyl alcohol, freed ofnon-polymeric materials and tested for oxidation resistance at 90° C.,along with control polymers, in the manner described in Example 7, withdifferent aminomercaptans identified in Tables I and II.

                  TABLE IX                                                        ______________________________________                                                           REACTION    O.R.                                                      AMINO   CONDITIONS  VALUES                                         SUBSTRATE    MER-      AIBN    TIME  AT                                       SOLUTION     CAPTAN    p.h.r.  HRS   90° C. HRS                        ______________________________________                                        cis-1,4-polybutadiene.sup.a                                                                --        --      --    9                                        cis-1,4-polybutadiene                                                                      MADA      0.40    41    445                                      cis-1,4-polybutadiene                                                                      MPDA      0.20    64    435                                      cis-1,4-polybutadiene.sup.b                                                                IV        0.25    64    380                                      cis-1,4-polybutadiene                                                                      V         0.25    64    60                                       cis-1,4-polybutadiene                                                                      VI        0.25    64    62                                       cis-1,4-polybutadiene                                                                      VII       0.25    64    62                                       cis-1,4-polybutadiene                                                                      XIV.sup.f 0.25    64    380                                      cis-1,4-polyisoprene                                                                       --        --      --    0.25                                     cis-1,4-polyisoprene                                                                       MPDA.sup.d                                                                              0.25    46    18                                       1,5-polypentenylene.sup.e                                                                  --        --      --    63                                       1,5-polypentenylene.sup.e                                                                  MPDA      0.40    64    81                                       ______________________________________                                         .sup.a A 5.00% benzene solution of a polymer having 97% cis1,4-structure.     .sup.b A solution of 100 parts of the same polymer in a mixture of 295        parts hexane and 585 parts benzene.                                           .sup.c A 5.00% benzene solution of a polymer having 96% cis1,4-structure.     .sup.d Using 4.00 parts of this compound.                                     .sup.e A 5.00% benzene solution of a polymer made by polymerizing             cyclopentene with a typical metathesis catalyst.                              .sup.f Described in Example 3.                                           

On the basis of results indicated in Table IX, it may be seen that theintrinsic resistance of the polymeric substrates were considerablyenhanced by interaction with an aminomercaptan.

EXAMPLE 10 Incorporation of MPDA into Butadiene/Styrene Copolymer DuringMilling and Curing

A commercial butadiene/styrene copolymer-SBR 1502 (containing 23.5%bound styrene), protected with 1.25 parts of the non-staining phenolicantioxidant Wingstay T, (product of the Goodyear Tire and RubberCompany) was compounded on a mill with the ingredients listed in TableX.

                  TABLE X                                                         ______________________________________                                        INGREDIENTS     PARTS BY WEIGHT                                               ______________________________________                                        SBR 1502        100                                                           Zinc oxide      15.0                                                          TiO.sub.2       30.0                                                          CacO.sub.3      24.0                                                          Sulfur          2.00                                                          2-Benzothiazolyl,                                                                             1.00                                                          N-morpholinyl disulfide                                                       MPDA            2.00                                                          ______________________________________                                    

The polymer was pressed into an 0.020 inch sheet and cured for 45minutes at 300° F. or to 90 per cent of optimum cure based on Monsantorheometer data. A control polymer, compounded similarly in absence ofMPDA was pressed into a similar sheet which was cured for 30 minutes at300° F. to the same cure level.

A series of one-inch strips was cut from each white vulcanizate. Somewere extracted repeatedly with 80/20 benzene/ethanol mixture at ambienttemperature over a 2-week period and then dried. Times for extractedstrips to absorb 1% by weight of oxygen at 100° C. were compared withtimes required by non-extracted strips.

It may be seen on the basis of data recorded in TABLE XI that whereasthe control SBR vulcanizate loses most of its resistance to oxidation byextraction of the antioxidant Wingstay T, that the SBR vulcanizatemilled and cured in presence of MPDA retains a very large percentage ofits originally higher resistance to oxidation after extraction becauseof the chemical incorporation of some of the MPDA into the vulcanizate.

                  TABLE XI                                                        ______________________________________                                                     O.R. VALUES AT 100° C.; HRS                               VULCANIZATE    UNEXTRACTED   EXTRACTED                                        ______________________________________                                        SBR-1502 Control                                                                              95            9                                               SBR-1502 compounded                                                                          250           170                                              with MPDA                                                                     ______________________________________                                    

EXAMPLE 11 Aminomercaptans as Conventional Antioxidants forButadiene/Styrene Copolymer

A butadiene/styrene copolymer was prepared by the method used forpreparation of SBR-1006. The latex was shortstopped at 70% conversionbut was not protected with commercial antioxidants. The latex wascoagulated with isopropyl alcohol, extracted free of non-polymericsubstances with hot isopropyl alcohol and vacuum evaporated. A 3%solution of copolymer in benzene was prepared. Batches of this cementwere charged with 2.00 levels of different aminomercaptans. Oxidationresistance of films made from these cement batches was determined at100° C. Such values are indicated in Table XII and compared withcontrols. The structures of the aminomercaptans are referred to in TableXII by Roman numerals indentified in Tables I or II.

It may be seen from Table XII that all of the aminomercaptans I, II, VIIand XIV, when uniformly distributed in small quantity in SBR, notcontaining any other antioxidant, considerably enhance the oxidationresistance of this polymer in the same manner that the commercialantioxidant Wingstay-L does when distributed in the same manner.

                  TABLE XII                                                       ______________________________________                                                              O.R. VALUES                                             AMINOMERCAPTAN CHARGED                                                                              AT 100° C., HRS.                                 ______________________________________                                        None                    0.5                                                   I                     415                                                     II                    415                                                     VII                   450                                                     XIV                   180                                                     1.00 part of Wingstay-L.sup.a                                                                       300-350                                                 ______________________________________                                         .sup.a A hindered phenolic antioxidant product of The Goodyear Tire and       Rubber Company.                                                          

Aminomercaptans described herein, some of which are novel compounds,serve as antioxidants to stabilize polymers against aging whendistributed throughout a polymer by conventional techniques as byaddition to a polymer cement or latex, by blending into a solid polymeron a mill or Banbury, or by mixing with a liquid polymer or solidpolymer powder. Such aminomercaptans include:

N-(4-anilino-phenyl)-α-mercaptoacetamide,

N-(4-anilino-phenyl)-β-mercaptopropionamide,

N-[4-(α',γ'-dimethyl-butylamino)-phenyl]-β-mercapto-propionamide and

N-(β-mercapto-β,β-dimethyl-ethyl), N'-phenyl-p-phenylene diamine

All of the compounds except the first are considered to be newcompounds. They have antioxidant properties. The last of the compoundshas some antiozonant properties as well.

I claim:
 1. A process for producing a polymer self-resistant to aging by an addition reaction, which process comprises interacting a polymeric substrate containing at least one reactable double bond per polymer molecule with from 0.1 to 10 parts by weight of an aminomercaptan selected from the group consisting of N-(4-anilino-phenyl)-β-mercaptopropionamide and N-(4-anilino-phenyl)-α-mercaptoacetamide in the presence of a free radical catalyst, wherein the polymeric substrate is polybutadiene.
 2. A process for producing a polymer self-resistant to aging by an addition reaction, which process comprises interacting a polymeric substrate containing at least one reactable double bond per polymer molecule with from 0.1 to 10 parts by weight of an aminomercaptan selected from the group consisting of N-(4-anilino-phenyl)-β-mercaptopropionamide and N-(4-anilino-phenyl)-α-mercaptoacetamide in the presence of a free radical catalyst, wherein the polymeric substrate is polyisoprene.
 3. A process for producing a polymer self-resistant to aging by an addition reaction, which process comprises interacting a polymeric substrate containing at least one reactable double bond per polymer molecule with from 0.1 to 10 parts by weight of an aminomercaptan selected from the group consisting of N-(4-anilino-phenyl)-β-mercaptopropionamide and N-(4-anilino-phenyl)-α-mercaptoacetamide in the presence of a free radical catalyst, wherein the polymeric substrate is a butadiene-styrene copolymer.
 4. A process as specified in claim 1 wherein the aminomercaptan is N-(4-anilino-phenyl)-α-mercaptopropionamide.
 5. A process as specified in claim 2 wherein the aminomercaptan is N-(4-anilino-phenyl)-α-mercaptopropionamide.
 6. A process as specified in claim 3 wherein the aminomercaptan is N-(4-anilino-phenyl)-α-mercaptopropionamide.
 7. A process as specified in claim 1 wherein from about 0.5 to 5 parts by weight of the aminomercaptan is utilized.
 8. A process as specified in claim 2 wherein from about 0.5 to 5 parts by weight of the aminomercaptan is utilized.
 9. A process as specified in claim 3 wherein from about 0.5 to 5 parts by weight of the aminomercaptan is utilized. 